Congestive heart failure (CHF) effects approximately 4.8 million Americans. About 400,000 new cases are diagnosed annually and the condition is responsible for approximately 200,000 deaths per year. These statistics, in conjunction with the approximately;1 million hospitalizations annually attributable to CHF, result in an annual expenditure on the order of $10 billion.
CHF represents a condition which occurs when heart function becomes insufficient to meet the needs of the vital systems and tissues of the body. The inability of the heart to pump sufficiently is correlated to the measured ejection fraction, which is the percent of the blood pumped out during each heartbeat. An ejection fraction of between 50% and 75% is considered normal. This inability can be caused by failure of one or more sides of the heart, typically the left but also the right side; such failure can result from systolic or diastolic dysfunction, and may be represented by an ejection fraction of less than 50% and a resultant backup of fluid and accumulation of fluid in the lungs. Although less common, right-sided heart failure will result in fluid backup that manifests in a swelling of the veins and surrounding body tissues, inadequate tissue perfusion, fatigue and poor exercise tolerance. In addition, heart failure can result from diastolic dysfunction. This can result from disorders such as hypertension, valvular disease, transient ischemia, infiltrative disorders or congenital conditions such as hypertrophic cardiomyopathy. Although there are cases of pure diastolic dysfunction from infiltrative disorders such as amyloidosis or fibrosis, heart failure patients often have a combination of both systolic and diastolic dysfunction contributing to CHF.
The underlying reasons for this failure in heart functionality are varied. Thinning and weakening of the ventricle walls leads to dilation and a loss of pumping ability (systolic dysfunction). Alternatively, loss of elasticity results in a stiffening, which may result in a diminished volume of the heart's chambers and loss of pumping capacity (diastolic dysfunction) and cardiac output. Additionally, abnormalities in the functioning of the heart's valves can lead to insufficient cardiac output, for which the body attempts to compensate by causing the heart to increase its heart rate, hypertrophy and/or dilate. The compensation mechanisms utilized by the body may lead to architectural changes in the form of remodeling (especially after MI) or adaptation of the heart muscle, ultimately leading to irrevocable loss of function. Related causes of cardiac failure may be one or more conditions such as coronary artery disease, ischemic heart damage, e.g. damage resulting from a heart attack, uncontrolled hypertension, the direct and/or indirect effects of diabetes on the heart, valvular heart disease, cardiomyopathy, autoimmune response, disease and abuse by external agents such as alcohol, tobacco, anabolic steroids, and the like.
Historically, the preliminary diagnosis of CHF requires a history and a physical examination during which the condition is often characterized by various signs and symptoms of intra-vascular and interstitial volume overload, including shortness of breath, irregular heart rate, abnormal heart rate and signs of edema. To determine the severity and prognosis of CHF and to more clearly characterize a particular patient's condition, further diagnostic tests are usually needed.
Tests which further illustrate the mechanical condition of the heart are often useful, such tests include, but are not limited to, exercise stress testing, electrocardiogram, radionucleidangiography, echocardiography, chest X-ray and angiography. Echocardiography is presently considered an important diagnostic test for CHF. By using ultrasound to provide real time imagery of the beating heart, valve function and blood flow through the heart can be readily ascertained. Systolic function and diastolic function or some combination thereof is determinable through echocardiography.
Laboratory tests including but not limited to blood and urine testing are often helpful. These may indicate abnormalities in liver function, kidney function, cholesterol levels; blood sugar levels, hemoglobin levels, thyroid hormone levels and ANP, BNP, pro ANP, pro-BNP.
The diagnostic methods for diagnosing and distinguishing CHF, as outlined above, require numerous steps, expensive technology, and trained personnel for their performance and subsequent analysis. Patients may also be exposed to risk of radiation from nuclear studies or invasive procedures, i.e. heart catheterization. If a method and device could be provided for distinguishing and diagnosing CHF via a simplified body fluid test, the results of which could be interpreted by a lay person, a long felt need would be satisfied.